The METAFOR project, funded by the Max‑Planck‑Gesellschaft under grant 031B0850B, ran from 1 February 2020 to 31 July 2023. Its goal was to create a microbial production platform based on the methylotrophic yeast Ogataea polymorpha that could convert carbon‑dioxide‑derived C1 compounds into value‑added products. The project was carried out in close cooperation with the Institute for Applied Microbiology (iAMB), the Chair of Bioprocess Engineering (AVT) and the Institute for Technical and Macromolecular Chemistry (ITMC) at RWTH Aachen, while the Max‑Planck‑Institutes for Terrestrial Microbiology (MPI‑TM) and for Molecular Plant Physiology (MPI‑MP) supplied expertise in enzyme and strain development and executed work package 2.
A central technical achievement of METAFOR was the development of a suite of genomic editing tools for O. polymorpha. These tools enabled precise manipulation of the yeast genome, allowing the introduction of heterologous pathways and the optimization of native metabolic routes. Building on this platform, the team engineered a synthetic formate‑assimilation pathway. By expressing a set of enzymes that convert formate into formaldehyde, the yeast was rendered formatotrophic, meaning it could use formate as a sole carbon source. This metabolic engineering step was crucial because formate, produced by biocompatible hydrogenation of CO₂, had previously been used only as an electron donor in fermentations. The new pathway allowed the yeast to grow on formate without prior purification of the substrate, thereby integrating the chemical CO₂‑hydrogenation step directly into the bioprocess.
In parallel, the project optimized methanol utilization, the natural substrate of O. polymorpha. Through iterative strain improvement, the researchers increased methanol uptake rates and reduced by‑product formation, thereby improving overall carbon conversion efficiency. The combination of methanol and formate as feedstocks was evaluated in fed‑batch cultivations, demonstrating that the engineered yeast could simultaneously metabolize both C1 compounds. While specific growth rates and product titers were not detailed in the report, the successful establishment of a formatotrophic strain and the demonstration of growth on mixed C1 substrates represent a significant step toward industrially relevant C1 bioconversion.
The integration of a biocompatible CO₂‑hydrogenation process was another key outcome. The team investigated hydrogenation conditions that minimized the use of harsh bases and solvents, thereby preserving yeast viability. The resulting formate stream could be fed directly into the fermentation, eliminating the need for downstream purification and reducing process complexity. This approach aligns with the bio‑economy concept of producing industrial chemicals from renewable resources while minimizing environmental impact.
Beyond the core technical milestones, METAFOR produced several ancillary results. The genomic editing toolkit has been made available to the broader research community, and the engineered strains have been deposited in public culture collections. The project also generated a detailed metabolic model of O. polymorpha that incorporates the new formate pathway, providing a foundation for future metabolic engineering efforts.
The collaboration structure of METAFOR exemplifies interdisciplinary integration. MPI‑TM and MPI‑MP focused on enzyme discovery and pathway design, iAMB and AVT contributed process engineering and scale‑up expertise, while ITMC supplied analytical chemistry support for monitoring CO₂‑hydrogenation products. The project’s timeline was tightly coordinated, with work package 2—encompassing strain construction, pathway validation, and process integration—completed within the scheduled period. The funding from the Max‑Planck‑Gesellschaft ensured that all partners could contribute specialized resources, from high‑throughput screening platforms to advanced fermentation facilities.
In summary, METAFOR delivered a functional microbial platform capable of converting CO₂‑derived C1 compounds into value products, achieved through the development of genomic tools, a novel formate‑assimilation pathway, and the integration of a biocompatible CO₂‑hydrogenation step. The collaborative effort among Max‑Planck institutes, RWTH Aachen research groups, and the funding agency laid a robust foundation for future industrial applications of C1 bioconversion.